1. Field of the Invention
This invention relates to a subbing layer for a lithographic printing plate and to a lithographic printing plate comprising such subbing layer exhibiting improved incubation stability and extended shelf-life.
2. Description of the Prior Art
One important characteristic of any presensitized lithographic printing plate is the ability to remain stable and yield reproducible speed performance between the time the plate is manufactured and subsequently used.
U.S. Pat. No. 4,086,092 describes a method of manufacturing presensitized lithographic printing plates demonstrating an extended shelf-life wherein a potassium zirconium fluoride solution is coated on the surface of an aluminum sheet. Thereafter, the aluminum sheet is treated with a sodium silicate solution.
U.S. Pat. No. 4,427,765 notes under column 4 that lithographic printing support materials prepared in accordance with known methods in many cases do not satisfy current printing requirements because after treatment with alkali metal silicates (which leads to good developability and hydrophilic character) a certain deterioration of the shelf-life of light-sensitive layers must be accepted.
U.S. Pat. No. 4,467,028 discloses a planograpic printing plate having an anodized metal substrate, a photosensitive layer and an interlayer comprising a hydroxy-substituted organic acid which minimizes background dye staining.
Thus, there is a need for lithographic printing plates exhibiting improved incubation stability and extended shelf-life.